The present invention relates to a lock. In particular, although not exclusively, the invention relates to a double-core type padlock for use with steel grilles. However, it will be appreciated, that the invention is not limited in its use with steel grilles and may have many and varied applications.
Taiwan Utility Model Application No. 84202129 is illustrated in FIG. 1 (prior art). The double-core horizontal lock includes a main body 10 and a lock block defining a locking space 16 therebetween. The main body 10 and the lock block have aligned bolt holes 13 extending therethrough. In the locked configuration illustrated in FIG. 2, a lock bolt 70 extends through the bolt holes 13. The lock bolt 70 has two spaced peripheral grooves 71, 72. In the locked position illustrated in FIG. 2, a latch tongue 21 of a latch member 20 engages within the adjacent groove 72. The latch member 20 is an elongate member slidable axially and biased towards the locking position by spring 24. The locking member 20 includes a side notch 22. Operable within the side notch is one end of a mother and daughter pin arrangement 40, 42. The conical end face of the mother pin 40 engages with a correspondingly inclined surface formed in the side notch 22 of the latch member 20. In the locked configuration illustrated in FIG. 2, the spring 24 urges the latch member 20 such that the latch tongue 21 will be received in the groove 72. However, during the unlocking step as the key is turned as illustrated in FIG. 1, the mother pin 40 will be pushed upwardly and the inclined mating faces will move relative to each other so as to push the latch member 20 against the bias of the spring 24. This pulls back the latch tongue 21 from the groove thereby releasing the lock bolt 70.
It can be seen from FIGS. 1 and 2 that the mother pin 40 only engages with the side of the latch member 20. There is only a small contact surface between the two members and so if the components are not machined with fine tolerances, the engagement surfaces might accidentally disengage. Or alternatively, jamming might occur. The arrangement therefore does not lend itself to heavy duty applications.